In effect, it is sometimes necessary, during a parachute jump, to disengage oneself from one's principal canopy which has, for example, opened badly. Once such release has been effected, the parachutist can then open his emergency parachute.
Such release is also desirable just after a landing under unfavourable atmospheric and/or environmental conditions, for example in wetland, on a tree, an electricity pole, or in the case of strong gusts of wind, in order thus to avoid the parachutist being swept along and/or dragged over the ground, after landing.
The prior art, and more precisely U.S. Pat. No. 4,337,913 and French Patent No. 2 772 339, discloses a safety device allowing the detachable connection between the principal canopy and harness of a parachute, said device comprising:                a riser, of longitudinal axis (X—X), presenting an upper part connected to said canopy and a primary loop connected to a primary ring;        a secondary loop, fixed on said upper part of said riser, connected to a secondary ring;        a flexible thong fixed to said riser and maintained by a cable locking this thong;        a harness ring fastened to said harness.        
The assembly is connected in the manner described hereinafter: the primary ring passes in the harness ring, then is folded on the riser, then the secondary ring is passed in the primary ring and likewise folded on the riser; this secondary ring is maintained by the flexible thong which itself is locked by the locking cable.
The object of the French and U.S. patents differs mainly by the form of the connection of the thong with the riser and the capacity, in the case of the French Patent, of allowing the riser to better oppose elongations due to the absence of weakening of its resistance by the boring for positioning an eyelet.
According to the two Patents mentioned above, the principal canopy of the parachute is thus released by the extraction of the cables locking the two release elements.
Due to the shape of the harness ring, the latter exerts during traction a lever arm on the primary ring which itself exerts a lever arm on the secondary ring which exerts a lever arm on the thong and causes it to be unlocked.
Unlocking of the thong then leads to a release of the riser, and therefore of the canopy.
The device according to the French Patent functions along the same principle as the device according to the U.S. patent.
In the two known devices described hereinabove, during the traction exerted on the harness ring, there is reduction of the effort applied, such reduction being determined by the diameter of the different rings.
The lever arm of each ring is also a function of the diameter of the ring and of the diameter of the torus constituting the ring.
Thus an increase in the reduction and of the lever arm makes it necessary to increase the diameter of the rings and to reduce, or not increase, the diameter of the torus constituting the rings.
Consequently, if it is desired to decrease the intensity of the effort to be applied at the level of the harness in order to be able to release the canopy, the diameter of the different rings must be increased.
This is difficult to effect beyond a certain limit because of the space requirement generated and the relative greater fragility of a ring of large diameter with a torus of small diameter.
Moreover, a large-diameter ring offers an orifice which may allow the undesirable passage of matter that may be detrimental to the correct functioning of the device.